Most of recent image forming apparatuses like MFPs (Multi-Functional Peripherals) have an imposition function to layout plural pages on one sheet. After printed sheets prepared by using the imposition function are cut into blocks of pages and then the pages are sorted, final printed products are produced. With the imposition function, it is capable of imposing multiple print jobs (referred to as ganging or ganging multiple print jobs), which allows a user to create final printed products of multiple print jobs with cost efficiency by printing multiple print jobs together on sheets with the imposition function and stacking and cutting the printed sheets together, as far as the location of cuts of the printed sheets are the same.
As an example of a technique to impose and print multiple print jobs, JP-A No. 2012-141668, which corresponds to United States Patent Application Publication No. US2012/0163891A1, discloses the following image forming apparatus. The image forming apparatus includes a main image forming section and an interleaf image forming section. The main image forming section imposes a plurality of jobs and generates at least one piece of main image data. The interleaf image forming section generates an interleaf image depending on the jobs of the main image data and generates interleaf image data including the interleaf image. The interleaf image forming section forms an image representing a color or pattern different from those of the jobs, in an area of the interleaf image data which corresponds to positions of side edges of the jobs of the main image data.
In ganging, which is a process of placing or imposing multiple print jobs at the respective positions on one surface of a sheet to impose the print jobs, the arrangement of the multiple print jobs is defined so that final printed products of the print jobs can be given after printing the print jobs on plural sheets and stacking and cutting the printed sheets together. When print jobs containing a different number of pages are imposed according to this arrangement, such an imposition makes a blank part (referred to as a blank page) at a position where a print job containing a fewer number of pages is assigned, on one or more imposed sheets, which causes waste of paper.
As one of conventional solutions for this matter, there is known a method of combining multiple print jobs into one print job and then imposing the resulting print job. This imposition method has the advantage of reducing useless blank pages but has the disadvantage of placing pages of two or more print jobs at the same job-imposing position on sheets in a mixed manner and therefore needing a complicated process of sorting the pages after cutting the sheets given after imposing and printing the multiple print jobs.